The destruction by nematodes, especially so-called root-knot nematodes, of valuable field crops presents a serious problem to agriculture. Field crops in need of protection from nematodes include soybeans, corn, peanuts, cotton, alfalfa and tobacco. In addition, vegetables, such as tomatoes, potatoes, sugarbeet, carrots and the like, as well as fruits, nuts, ornamentals and seed bed crops such as apples, peaches, peas, citrus fruit and grapes may also require protection from the ravages of nematodes.
In the past, control of nematodes has generally required the application of chemical nematicides to fields. However, nematodes have exhibited a tendency to develop immunity to most chemical nematicides. Moreover, in many instances, such application of chemical nematicides to fields is environmentally undesirable.
Although it would be desirable to employ natural means, particularly nematophagous fungi, to control nematodes, in the past attempts to employ such fungi in non-sterile soil have proved to be ineffective. Nematophagous fungi are generally divided into two catagories, i.e., (1) nematode-trapping fungi which produce mechanical or adhesive traps: and (2) endoparasitic fungi which infect nematodes when their conidia (spores) are ingested or adhere to the cuticle of the worms.
R. Mankau, in "Soil Fungistasis and Nematophagus Fungi", Phytopathology, 52, 611-615 (1962) notes that "several unsuccessful attempts have been made in the past to introduce nematode-trapping fungi into soil and effect a biological control of plant-parasitic nematodes", although he states that one group of researchers have demonstrated "a moderate, but statistically significant, reduction of nematode injury to pineapple plants". R. Cooke, in "Relationships between Nematode-Destroying Fungi and Soil-Borne Phytonematodes", Phytopathology, 58 909-913 (1968), draws a similar conclusion about nematode-trapping fungi indicating that "the arbitrary addition of fungi or organic amendments to soil is likely to prove no more fruitful in the future than it has in the past".
Past experience with endoparasitic nematophagous fungi has generally indicated that the application of these species would similarly not control nematodes to any desirable degree. Thus, A. Y. Guima et al in "Potential of Nematoctonus Conida for Biological Control of Soil-Borne Phytonematodes", Soil Biology and Chemistry, 6, 217-220 (1974), indicate that although some nematode control was achieved in sterilized soil, "natural nematode populations in non-sterile soil were not affected by the introduction of Nematoctonus (i.e., N. concurrens and N. haptocladus--both of which are endoparasitic fungi) conidia even at the highest spore concentrations (i.e., 1.25.times.10.sup.5 spores per gram of moist soil)".
Thus, it is completely unexpected that the application of a composition comprised of (a) Meria coniospora fungus spores and (b) a suitable nonliving carrier to the soil will significantly reduce nematode infestation, even when said spores are present in ratios as small as 2 spores per nematode egg are added. This degree of control is even more unexpected in view of the disclosure in "Attraction of Nematodes to Endoparasitic Nematophagous Fungi", H. Jansson, Trans. Br. mycol. Soc., 79 (1) 25-29 (1982) that although nematodes are attracted to conidia of M. coniospora a concentration of 0.5.times.10.sup.6 spores per microliter was necessary to attract nematodes.